Sen. Mark Kirk, reacting to reports that the crash of a Malaysian airliner in eastern Ukraine earlier today was caused by a surface-to-air missile, took to Twitter this afternoon to call for expanded sanctions on Russia in response to the incident.

“Russian-made advanced SAM has murdered 295 innocent people,” the Illinois Republican wrote in a tweet. “Over-due Russian sanctions should expand to oil and energy sectors.”

U.S. officials have not confirmed assertions that the crash, which killed all 295 people aboard, including 23 U.S. citizens, was caused by a missile strike.

Danielle Varallo, a spokeswoman for the senator, said Kirk was relying on press reports that suggest the crash was caused by a missile when he and staff members composed the tweet.

“I believe it was from a press report,” Varallo said.

Ukrainian officials have been widely quoted in press reports suggesting that Russian-backed rebels shot down the plane.

Ukrainian President Petro Poroshenko tweeted earlier today that the crash of flight MH17 “is not an incident or a catastrophe, it is a terrorist attack.” And Ukrainian Interior Ministry official Anton Gerashchenko said on Facebook that “terrorists using a Buk anti-aircraft system kindly given to them by Putin have shot down a civilian airliner flying from Amsterdam to Kuala Lumpur.”

News of the incident came as President Obama and Russian president Vladimir Putin were discussing a new round of economic sanctions that the U.S. and EU partners imposed on Moscow yesterday.